Fig. 3.

Increased abundance of CSTB protein in fibroblasts isolated from individuals who have trisomy of Hsa21 is not sufficient to decrease total or lysosomal cathepsin activity compared to disomic matched cells. Cathepsin B activity and CSTB protein abundance were measured in human primary fibroblasts. a, b Trisomy of chromosome 21 significantly increases CSTB protein abundance as measured by western blot (Mann–Whitney U test p = 0.0286). c Trisomy of chromosome 21 does not alter total cathepsin B activity as measured by biochemical assay (rate of cleavage of Ac-RR-AFC), (Mann–Whitney U test p = 0.8857) or d by BMV109 fluorescence (red) quantified by in gel assay based upon enzyme identification by molecular weight (28 kDa) normalized to total protein measured by Coomassie blue (Mann–Whitney U test p = 0.6857). e Trisomy of Hsa21 does not alter cathepsin activity within lysosomes as measured by lysotracker (cyan) colocalised BMV109 fluorescence (magenta) (Manders’ coefficient (disomic) = 0.302; (Trisomy 21) = 0.339) (Mann–Whitney U test p = 0.2000). Individual data points are group means for n = 4 disomic and n = 4 trisomy 21, independent cells lines (three technical replicates for western blots and 15–20 cells per lines for immunofluorescence), error bars SEM, p < 0.05